The present invention relates to an automatic instrument for testing bearing and more particularly to an instrument for performing a test known as tympanometry.
Tympanometry is an objective method for evaluation of the mobility of the tympanic membrane and the functional condition of the middle ear and is the measurement of eardrum compliance change as air pressure is altered in the external auditory canal. These measurements are recorded on a graph which represents the compliance-air pressure function and which is known as a tympanogram.
A point of significance is that the tympanic membrane is at maximum compliance when the air pressure in the middle ear is equal to the air pressure in the external ear canal. Tympanometry provides an indirect measure of existing middle ear pressure by identifying the air pressure in the external auditory canal at which the eardrum shows its maximum compliance. For example, patients who have intact tympanic membranes, with no middle ear pathology and adequate eustachian tube function, will show maximum compliance on the tympanogram at atmospheric pressure or within 50 mm of atmospheric pressure. Patients with intact eardrums and poorly functioning eustachian tubes, will show maximum compliance of other air pressure values.
To obtain a tympanogram, a probe is placed in the patient's ear which is initially clamped into a position of poor mobility by introducing positive pressure (+200 mm H.sub.2 O) into the external ear canal. Then the air presure in the external ear canal is systematically reduced while changes in the compliance are observed and recorded. As the air pressure is reduced, The eardrum becomes more compliant. When the air pressure in the external canal is exactly the same as the air pressure in the middle air cavity, the compliance reaches its optimum.
As the air pressure is further reduced beyond the point of maximum compliance, an unbalance of air pressure on either side of the tympanic membrane is created and the eardrum begins to show reduced compliance again.
The clinical uses of tympanometry are many. This technique demonstrates abnormalities in the mobility of the tympanic membrane due to stiffness, flaccidity, or the presence of fluid in the middle ear cavity. The technique of tympanometry can be used to monitor healing of tympanic membrane grafts, post-stapedectomy cases, or follow-up of otitis media.
The apparatus of this invention is an instrument which performs the above described evaluation in an automated sequence providing the results in the form of a recording or tympanogram. The instrument permits an efficient and rapid test program to be carried out for groups, such as groups of school children, by relatively inexperienced personnel and in a manner which provides an easily read and preservable record of the test procedure. This makes an important hearing test available in a practical way for almost universal use and for use with younger persons since the automatic test requires no response from the patient.
Accordingly, an object of the present invention, therefore, is to provide an improved automatic apparatus for tympanometry.
Another object of the invention is to provide a fully automated means for tympanometry providing test results not requiring a response from the patient.
Another object of the invention is to provide an improved instrument for tympanometry permitting relatively rapid and reliable testing.
Another object of the invention is to provide an automatic tympanometric test means providing a recorded read-out.
Another object of the invention is to provide an apparatus for tympanometry which may be utilized by relatively inexperienced personnel for testing large numbers of patients.
Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.